The invention relates to readout systems for segmented detectors, including pixel arrays, and more particularly to pulse shapers, including timing circuitry, therefor.
The introduction of pixel detectors in tracking applications has set the demand for high density readout electronics consisting of one cell per pixel with the task of identifying the address of the pixels where signals above a preset threshold are recorded. The same readout electronics associated with a histogramming memory to build-up the distribution of counts recorded by each pixel in a fixed time interval is employed in imaging applications. In either case, only the presence of a signal is recorded by the readout system.
There are, however, situations, where signal-related parameters are to be extracted and a readout that is able to acquire and process multiparametric information is required. For example, if the value of the charge associated with the signal is available, it is possible to increase the position resolution well beyond the geometric size of the pixel by using an interpolation approach.
Signal timing is important in several time-resolved or time-correlated position sensing and imaging applications. Examples of situations requiring both position and time information are provided by Time-of-Flight mass spectroscopy and by the analysis of reactions initiated by photo-ionization (molecular dissociation), where the photoionization produced by laser light results in fragmentation. Multi hit time-resolved detection may be required in this case. Another example of a situation demanding accurate timing is three dimensional imaging based upon time-domain reflectometry associated with a pixel matrix.
The idea of multiparametric acquisition from pixel matrices can be extended to more complex cases including other signal features, for instance, shape-related parameters.
One particular type of system intended to readout multiparametric information from a matrix of pixels acquires the charge associated with the signal and provides timing information from each pixel. Although it lends itself to a broad range of time-correlated imaging situations involving any kind of pixel matrices, a particular application is to pixels that sense the output charge distribution from a Micro Channel Plate (MCP). The combination of a microchannel plate and a pixel matrix is an extremely versatile detector and the readout system must be able to fully exploit the intrinsically high position resolution and time accuracy featured by the MCP.
The invention is a system to readout multiparametric information from a matrix of pixels or other segmented detector. The system acquires charge associated with a signal and provides timing information from each pixel or other detector segment. Although it can be used in a broad range of time-correlated imaging situations involving any kind of pixel matrices, the system particularly applies to pixels that sense the output charge distribution from a Micro Channel Plate (MCP). The combination of a microchannel plate and a pixel matrix is an extremely versatile detector and the readout system must be able to fully exploit the intrinsically high position resolution and time accuracy featured by the MCP. The readout system of the present invention meets these requirements and provides a significant functional improvement over conventional pixel systems.
The invention includes a pulse shaper implemented in monolithic CMOS with a delay unit formed of a unity gain buffer. The shaper is formed of a difference amplifier having one input connected directly to an input signal and a second input connected to a delayed input signal through the buffer. The invention also includes an elementary cell based on the pulse shaper and a timing circuit which gates the output of an integrator connected to the pulse shaper output. The invention further includes a detector readout system formed of a plurality of elementary cells, each connected to a pixel of a pixel array, or to a microstrip of a plurality of microstrips, or to a detector segment.